How to Safely Update UI Controls from Non-UI Threads in C#?

C# cross-thread operation verification: accessing controls from non-UI threads

When accessing UI elements (such as TextBox) in a thread other than the thread that created the control, you may encounter the exception: "Invalid cross-thread operation: Accessing control 'textBox1' from a thread other than the thread that created it". This is because each UI element is associated with a specific thread for handling events and modifications.

In this example, you are trying to update the serialport1_DataReceived control from the textBox1 event handler, which executes on a separate thread due to the asynchronous nature of serial port operations.

Solution:

To resolve this issue and safely access the textBox1 control from a non-UI thread, you need to ensure that all interactions with UI elements are called on the main (UI) thread. This can be achieved using a scheduler, which provides a cross-thread communication mechanism and ensures that UI updates are performed on the correct thread.

The following is a modified version of the textBox1 method using the delegated security update serialport1_DataReceived control:

private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
  // 在UI线程上更新'txt'变量
  txt += serialPort1.ReadExisting().ToString();

  // 使用委托在UI线程上访问'textBox1'控件
  SetTextCallback d = new SetTextCallback(SetText);
  this.Invoke(d, new object[] { txt.ToString() });
}

private delegate void SetTextCallback(string text);

private void SetText(string text)
{
  // 检查'textBox1'控件是否在不同的线程上创建
  if (this.textBox1.InvokeRequired)
  { 
    this.Invoke(d, new object[] { text });
  }
  else
  {
    // 如果在UI线程上创建，则直接更新'textBox1'控件
    this.textBox1.Text = text;
  }
}

With this approach, you ensure that textBox1 controls are always accessed and modified on the main (UI) thread, thus resolving cross-thread operation exceptions.

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